From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B3C4AD29FEF for ; Wed, 14 Jan 2026 11:27:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 167D86B0089; Wed, 14 Jan 2026 06:27:51 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 13D926B008C; Wed, 14 Jan 2026 06:27:51 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 05C7D6B0092; Wed, 14 Jan 2026 06:27:50 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id E84C86B0089 for ; Wed, 14 Jan 2026 06:27:50 -0500 (EST) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id A61BC1AD9A3 for ; Wed, 14 Jan 2026 11:27:50 +0000 (UTC) X-FDA: 84330344700.10.2A843A7 Received: from out-179.mta0.migadu.com (out-179.mta0.migadu.com [91.218.175.179]) by imf07.hostedemail.com (Postfix) with ESMTP id 0AE3A40003 for ; Wed, 14 Jan 2026 11:27:48 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=SZlQyonb; spf=pass (imf07.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.179 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1768390069; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=YuZ8qO/NM8znoBBhdw/uXBM5t31I/Z9zioYjWeQuJrs=; b=VoCu+TAHv4UFPL2J8a0qJosVdMzu5ZPsJzit/zYhoCqnMkb1LWer5H+A2GTAsNIEs7+Goi BoI021doIRRZLCRmsM+w6jSVjU8+Lq9AsXZN/Cxk8WSEDk1cAf74FalndtH3OnTijfem+r l+pzSuXPUUi/ShV+uy/MSfoPkdsoRxs= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=SZlQyonb; spf=pass (imf07.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.179 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1768390069; a=rsa-sha256; cv=none; b=y4dpD41V0ZOdLLZetXyga3uV65t6SVl4t/xWk58BrTE+Il+2yXpfJa6FHfDctO7QV/06Ob q2im9di+Tg9pCF4lTUGoIYa3sB0kYSUx3ITscLe32GND3vdtpj9+rnsS+HCFBkz21Q+c4L Q1i4A6R50Vq1ViipKSHmOHGAYJlohC4= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1768390065; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=YuZ8qO/NM8znoBBhdw/uXBM5t31I/Z9zioYjWeQuJrs=; b=SZlQyonb45fCebG0YQSYRpzD3FY/6UP6cIs/1wIrwWaMQbW2ihRA0cBTcI3QiMnOK88MFs BgFbkvVmyphkjYaouhv4utI+JLAKapBep2vbEbxCtcS+nM80eRo8L0Ma670qvEjvP7nBx1 ++6Z3C56HhaRTiG39atgCCDhVazg0Oc= From: Qi Zheng To: hannes@cmpxchg.org, hughd@google.com, mhocko@suse.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, david@kernel.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, harry.yoo@oracle.com, yosry.ahmed@linux.dev, imran.f.khan@oracle.com, kamalesh.babulal@oracle.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, chenridong@huaweicloud.com, mkoutny@suse.com, akpm@linux-foundation.org, hamzamahfooz@linux.microsoft.com, apais@linux.microsoft.com, lance.yang@linux.dev Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng , Chen Ridong Subject: [PATCH v3 01/30] mm: memcontrol: remove dead code of checking parent memory cgroup Date: Wed, 14 Jan 2026 19:26:44 +0800 Message-ID: <290890d5739df2cb2d0e5a40e15f5e836fa65587.1768389889.git.zhengqi.arch@bytedance.com> In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 0AE3A40003 X-Stat-Signature: usndzg9not4a33eau5sbq8q635164jk7 X-HE-Tag: 1768390068-430416 X-HE-Meta: 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 FSOwrJWg 8RbToDlzkRJhW5uVd893TvYnqta+uGR2PRJi1P/nSTDRvSCsQxudo9EixNxnXLJnPwTpWwRp2dcIG6LYjSCfvYkWS4scgOMSeBe+FsVvcErot9Kg+Bij2e0uYWGHliunxXidsUA8X1FHNn9NJJIf7CYyjPBTsxKuu/sogRk8U+uARw94BQaJ14lW/tidO8mdVrD3XsODaABRbZFyDHrfHVIiEQrS9qhya54gd9e+BpqEnwbeh+QkbtTlYy0hGgbDkFT3brPYhJmLq7LDvO4Umxp5+1EW/BiJ1ZM9S X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Muchun Song Since the no-hierarchy mode has been deprecated after the commit: commit bef8620cd8e0 ("mm: memcg: deprecate the non-hierarchical mode"). As a result, parent_mem_cgroup() will not return NULL except when passing the root memcg, and the root memcg cannot be offline. Hence, it's safe to remove the check on the returned value of parent_mem_cgroup(). Remove the corresponding dead code. Signed-off-by: Muchun Song Acked-by: Roman Gushchin Acked-by: Johannes Weiner Signed-off-by: Qi Zheng Reviewed-by: Harry Yoo Reviewed-by: Chen Ridong Acked-by: Shakeel Butt --- mm/memcontrol.c | 5 ----- mm/shrinker.c | 6 +----- 2 files changed, 1 insertion(+), 10 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index f9455b4790ba5..c68af9fea0abd 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3352,9 +3352,6 @@ static void memcg_offline_kmem(struct mem_cgroup *memcg) return; parent = parent_mem_cgroup(memcg); - if (!parent) - parent = root_mem_cgroup; - memcg_reparent_list_lrus(memcg, parent); /* @@ -3645,8 +3642,6 @@ struct mem_cgroup *mem_cgroup_private_id_get_online(struct mem_cgroup *memcg) break; } memcg = parent_mem_cgroup(memcg); - if (!memcg) - memcg = root_mem_cgroup; } return memcg; } diff --git a/mm/shrinker.c b/mm/shrinker.c index 4a93fd433689a..e8e092a2f7f41 100644 --- a/mm/shrinker.c +++ b/mm/shrinker.c @@ -286,14 +286,10 @@ void reparent_shrinker_deferred(struct mem_cgroup *memcg) { int nid, index, offset; long nr; - struct mem_cgroup *parent; + struct mem_cgroup *parent = parent_mem_cgroup(memcg); struct shrinker_info *child_info, *parent_info; struct shrinker_info_unit *child_unit, *parent_unit; - parent = parent_mem_cgroup(memcg); - if (!parent) - parent = root_mem_cgroup; - /* Prevent from concurrent shrinker_info expand */ mutex_lock(&shrinker_mutex); for_each_node(nid) { -- 2.20.1